Michael Kuchka, Ph.D.
111 Research Drive, B220
Bethlehem, PA 18015
About my research...
Our lab studies the unicellular eukaryotic alga Chlamydomonas reinhardtii (Chlamydomonas website). Chlamydomonas has been used for decades as a model organism to study a wide range of research topics including organellar gene expression, the development and regulation of the photosynthetic electron transfer chain, flagellar assembly and cellular motility, and regulation of metabolic pathways. The organism is amenable to standard genetic analysis, a large collection of mutant strains is available, standard crosses can be done to define genetic loci and make different allelic combinations of genes, and genes can be cloned by complementation. The Chlamydomonas genome has been completely sequenced and annotated.
Chlamydomonas cells have a single chloroplast and can grow photosynthetically in a manner that is identical to that used by higher plants. They can also grow “heterotrophically” by metabolizing simple carbon sources such as acetate. Acetate is built into larger carbohydrates initially through the reactions of the glyoxylate cycle. This cycle partially overlaps with the Tricarboxylic Acid (TCA) cycle but its two key enzymes [isocitrate lyase (ICL) and malate synthase (MS)] bypass the two oxidative reactions of the TCA cycle that evolve carbon dioxide. The Chlamydomonas genome has multiple copies of genes encoding the enzymes of the glyoxylate cycle, highlighting the importance of this metabolic pathway to the cell.
RESEARCH QUESTIONS: Why does the Chlamydomonas genome have more than one copy of glyoxylate cycle genes? Do the encoded proteins work in different ways? Are they located differently in cells? Where does the glyoxylate cycle occur in Chlamydomonas cells?
We are also interested in how the glyoxylate cycle is used and regulated by Chlamydomonas cells. As an example, Chlamydomonas cells dramatically redirect their metabolism when deprived of nitrogen. Such cells accumulate oils in the form of triacylglycerols at high concentrations in their cytoplasm. Some researchers are using this as a potential and inexpensive source of biofuels. One of the ways that Chlamydomonas cells accomplish this metabolic shift is by down-regulating the expression of ICL and MS genes.
RESEARCH QUESTION: How are the genes encoding proteins involved in the glyoxylate cycle regulated in Chlamydomonas cells?
We have isolated a collection of Chlamydomonas mutants that are deficient in acetate uptake and/or assimilation. These mutants show interesting phenotypes that suggest unexpected features of glyoxylate cycle utilization and acetate metabolism.
RESEARCH QUESTION: What genes are impacted in these mutants?
We are currently using molecular biological, genomic, and bioinformatics approaches to identify these genes and determine the function of their gene products.
Godfried Sie, C., Hesler, S., Maas, S., and Kuchka, M. (2012) IGFBP7's susceptibility to proteolysis is altered by A-to-I RNA editing of its transcript. FEBS Letters, 586: 2313 - 2317.
Godfried Sie, C. P. and Kuchka, M. (2011) RNA Editing Adds Flavor to Complexity. Biochemistry (Mosc), 76: 869 - 881.
Rattanachaikunsopon, P., C.
Rosch, and M. R. Kuchka (1999). Cloning and characterization of the nuclear
AC115 gene of Chlamydomonas reinhardtii. Plant Molecular Biology,39: 1-10.
Yohn, C., A. Cohen, C. Rosch,
M. R. Kuchka, and S. P. Mayfield.(1998).Translation of the chloroplast
psbA mRNA requires the nuclear-encoded poly(A)-binding protein, RB47.
Journal of Cell Biology, 142: 435-442.
Wu, H. and M. R. Kuchka (1995).
A nuclear suppressor overcomes defects in the synthesis of the chloroplast
psbD gene product caused by mutations in two distinct nuclear genes of
Chlamydomonas. Current Genetics, 27: 263-269.
Rochaix, J.-D., M. Goldschmidt-Clermont,
Y. Choquet, M. Kuchka, and J. Girard-Bascou (1991). Nuclear and chloroplast
genes involved in the expression of specific chloroplast genes of Chlamydomonas
reinhardtii, in Plant Molecular Biology (ed. R. G. Herman) Plenum Press,
New York, NY.
Kuchka, M. R., M. Goldschmidt-Clermont,
J. vanDillewijn, and J.-D. Rochaix (1989). Mutation at the nuclear NAC2
locus of C. reinhardtii afects the stability of the chloroplast psbD transcript
encoding polypeptide D2 of photosystem II. Cell, 58: 869-876.
Rochaix, J.-D., M. Kuchka,
S. Mayfield, M. Schirmer-Rahire, J. Girard-Bascou, and P. Bennoun (1989).
Nuclear mutations affect the synthesis or stability of the chloroplast
psbC gene product in Chlamydomonas reinhardtii. EMBO Journal, 8:
Day, A., M. Schirmer-Rahire,
M. R. Kuchka, S. P. Mayfield, and J.-D. Rochaix (1988). A transposon with
an unusual arrangement of long terminal repeats in the green alga Chlamydomonas
reinhardtii. EMBO Journal, 7: 1917-1927.
Kuchka, M.R. and Jarvik, J.W. (1987). Short-Flagella Mutants of Chlamydomonas reinhardtii. Genetics 115: 685-691.
Kuchka, M. R., S. P. Mayfield,
and J.-D. Rochaix (1987). Nuclear mutations specifically affect the synthesis and/or
degradation of the chloroplast-encoded D2 polypeptide of photosystem II
in Chlamydomonas reinhardtii. EMBO Journal, 7: 319-324.
Kuchka, M.R. and Jarvik, J.W. (1982). Analysis of Flagellar Size Control Using a Mutant of
Chlamydomonas reinhardtii with a Variable
Number of Flagella. The Journal of Cell Biology, 92: 170-175.